Decorative glulam is largely used in kitchen bench tops. Other common uses are bar tops, stair treads and stringers, kitchen cabinet doors, seats, coffee tables, etc.
Used decoratively, glulam does not require structural strength, but rather aesthetics, durability, and hardness. The quality of the finish is of paramount importance, as the product is visible at all times and the performance of the glulam is also of primary importance. The product must be stable and without defect.
The quality assurance system is intrinsic in achieving a consistent and reliable product and a number of the GLTAA members specialise in this product area.
Structural glulam for use in primary structural members in domestic, commercial, and industrial buildings is produced by most of the GLTAA members.
Depending on location, the timber species used in the manufacturing process differs from producer to producer. In the west, the predominant timber species is Jarrah, in the south east, Tasmanian Oak and Radiata Pine and in the north east, Spotted Gum, Slash Pine and other mixed hardwoods, such as Blackbutt, Iron Bark, Sydney Blue Gum, etc.
In the past, this widely varying resource has created difficulties in trying to standardise glulam as a structural product. The milling procedure differs from mill to mill, and from species to species and the result has been that each producer has manufactured glulam of differing mechanical properties and of differing depths and widths. Designers were unsure of which properties and sizes were compatible, available and economic and the variance caused them problems in designing glulam.
As a result, the glulam manufactured by the GLTAA members has now been rationalised in order to establish a set of industry standard properties and corresponding sizes. The table below shows the GLTAA Glulam Mechanical Properties.
The designation of each group relates to the short duration stiffness (in GPa). The standard section sizes relating to each mechanical property group are available on request from members. These section sizes are the finished sizes of the glulam supplied. It is important for designers to note, that the correct designation be nominated on drawings, e.g. 315x85 GL18.
This makes the suppliers, builders, checkers and inspectors aware that the beam is to be an accredited section of known size and grade. It allows all producers capable of producing the grade of glulam to price the project without the designer having to make the decision to specify a one supplier product. The designation noted may be followed with a timber species if the designer requires a specific appearance. It should also be followed with a `C' for cambered (600M Industry Standard Radius) or an `S' for straight beams.
Producers nominated in their accreditation procedures which glulam properties they produce. The make up of the glulam may be in any configuration, so long as the grade and size of the glulam match that designated.
CHARACTERISTIC STRENGTHS AND ELASTIC MODULI FOR HORIZONTALLY LAMINATED GLULAM GRADES
NOTE: Glulam grade designations are based on the modulus of elasticity. Each of the grades may be relevant to specific products. Further information should be sought from appropriate industry associations